in the grip of an evil spirit
The significance of this figure to me is as a type of me (and perhaps you) or of the nation to which I (we) belong.
Theologically we serve God-- or the devil (there's certainly a grey area, on the fence, indeterminte, some good, some bad). But what I (we) do less than God is readily seen as an evil spirit.
I am many- Legion. Or more properly Legion is within me. It causes me to cut myself on the stones: the law, preconceived notions of what is good for us (but not for them). Separating ourselves from the rest of the world like all those with evil spirits do.
Thankfully we, too may be blessed with the healing seen in this story. I have been so blessed, am being blessed, and will be blessed. Hurrah!